Lubricating oil composition



Patented Jan. 9, 1940 UNITED STATES 2,186,346 LUBRICA'I'ING omCOMPOSITION Vernon L. Ricketts, Oakland, Calif., assignor to ShellDevelopment Company, San Francisco, Calif., a corporation of Delaware NoDrawing.

Application September 18, 1937, 4

Serial No. 164,576

12 Claims.

This invention relates to an improved lubricating oil especially adaptedfor use in Diesel engines, dealing with mineral lubricating oilscontaining small quantities of a salt or salts of certain aromaticderivatives of higher fatty acids and metallic or amphoteric polyvalentelements.

It is known that Diesel engines place an extremely heavy burden'onlubricating oils which are circulated through their internal lubricatingsystems during operation. Upon prolonged use of a lubricating oil in aDiesel engine, piston rings develop a tendency to stick, possibly due tothe accumulation of products of oxidation such as tar, coke, etc., orfor other reasons. Stuck piston rings cause blow-by and result in lossof power, waste of fuel, rapid destruction of the lubricating oil anddamage to the engine.

In order to overcome piston ring sticking, small amounts of certainorganic salts of calcium, such as described in the Vobach Patent2,081,075, have been added to lubricating oils. It has been found,however, that the suitability and the effectiveness of compounds of thistype vary with the aromatic grouping attached to the fatty acid radicalof the salt, as well as with the metal which they contain. For instance,whereas the calcium salt of phenyl stearic acid is useful for thepurpose, the corresponding salt of magnesium forms gels with mineraloils and is entirely unsuited. On the other hand as explained furtheron, if the phenyl group is not attacheddirectly to the carbon chain ofthe fatty acid, but instead is linked thereto as a side branch throughone or more intermediate aliphatic carbon atoms, acids are obtained, themagnesium and certain other salts of which are exceptionally effectiveas ring sticking inhibitors and do not cause gelling when used in theamounts required to inhibit piston ring sticking.

Accordingly I have discovered that compounds 40 which. are especiallysuited for inhibiting ring sticking and carbon deposition in Dieselengines comprise salts or salt-like compounds of polyvalent metallic andamphoteric elements, and more particularly the salts of light metalssuch as calcium, aluminum and especially magnesium of higher fattyacids, which acids have attached to their carbon chain anaromatic'grouping as a side branch through an aliphatic link of one 50or more carbon atoms.

Higher fatty acids as herein defined are those which are substantiallystable under conditions 7 of lubrication, i. e., which do notpolymerizeor oxidize excessively to form resins, and which 55 contain atleast 10 carbon atoms, 12 to 22 carbons in straight chains being mostdesirable. The fatty acids may be saturated or mono-olefinic, and maycontain substantially neutral substitution radicals'such as OH radicals.Suitable fatty acids are for instance lauric, palmitic, 5

stearic, arachidic, oleic, ricinoleic, ctc., acids.

The aliphatic link which connects the aromatic grouping with the fattyacid carbon chain may be paraflinic or mono-olefinic andshould containpreferably not more than 3 carbon atoms. 10 It may advantageously, butnot necessarily, be attached to the fatty acid carbon chain incloseproximity, such as an alphaposition, in regard to the carboxyl radical.

The aromatic grouping comprises hydrocarbon 15 groups such as phenyl,naphthyl, tetra hydronaphthyl, anthracyl, etc., to which may be attachedone or more alkyl, radicals preferably of not more than 3 carbons each.

The general formula of my compoundsis 7 where M is a polyvalent metallicor amphoteric" element, preferably a light weight metal having aspecific gravity below about 4; and R. com.- prises an aliphatic carbonchain containing not more than one double bond and an aromatichydrocarbon grouping attached thereto as a side branch through analiphatic link of one or more carbon atoms, preferably in closeproximity to the carboxyl radical.

My compounds may be obtained by reacting a higher fatty acid with anaromatic aldehyde un- 36' der conditions to effect a condensation withsimultancous liberation of water. "The general type of reaction involvedmay be illustrated as follows:

R CH2CO0H+R1C RrC-COQH'FHIO.

In this reaction I have indicated that the substitution' takes place inalpha position to the 45. carboxylradical, the theory being that thecarboxyl radical activates the alpha carbon. This, however, isnotnecessarilythe case,. and the condensation may take place at some othercarbon atom particularly if the carb'on chain con.-

tains a double bond and/or substitution radicals, which may activateothercarbons of the chain and introduce factors affecting the relativereactivities of the several carbon atomsln' an incalculablermanner.Moreover when checking the degree of unsaturation of typicalcondensation products by meansof iodine absorption, the theoreticaldegree of unsaturation was not always confirmed, and yet the acids soproduced were equally as effective for ring sticking inhibiting purposesas the pure compounds which had condensed in accordance with the aboveequation and possessed the theoretical iodine numbers.

A typical example of producing one of the acids of my invention is asfollows:

300 parts by weight of calcium stearate, 106 parts of benzaldehyde and450 parts of acetic acid anhydride were heated to about 280 F. for 8hours. The resulting mixture was then distilled at atmospheric pressureto remove acetic acid anhydride. The distillation residue was thentreated with an excess of aqueous hydrochloric acid, and the upper layercontaining alpha-benzalstearic acid was separated and washed with waterto free it from acetic acid. The yield of alpha-benzalstearic acid was75% of the theoretical.

If desired the double bond created by the condensation reaction may bereduced to yield a saturated bond. Thus the benzalstearic acid of theabove example was dried, dissolved in absolute ethyl alcohol and treatedwith 100 parts metallic sodium at l30-150 F. for three hours. Afterthis, the benzalstearic acid was completely reduced to the equivalentbenzyl compound.

The amounts of the salts herein described, required successfully toinhibit or retard ring sticking are quite small and usually vary between.5 and 2.5% of the lubricating oil, although smaller or larger amountsmay be added.

As pointed out before one of the advantages of certain of my salts of myacids over similar salts of other aromatic fatty acids heretoforeemployed for ring sticking inhibition, resides in the fact that thesalts of this invention produce non-gelling blended oils when added tohydrocarbon oils in ring sticking inhibiting'quantities. Moreover, Ihave found that in general my salts are more soluble in hydrocarbon oilsand less corrosive and/or abrasive than similar known salts.

When comparing the ring sticking inhibiting powers of the variouspolyvalent metallic, and

, ring sticking has been known to occur with a lubricating 011containing a like amount of the calcium salt near 1000 hours ofoperation, and a heavier salt such as the barium salt, permittedoccasional ring sticking after about 250 hours running of the engine. Inthe absence of any salt, ring sticking normally. occurred in less thanhours under the standardized conditions of the tests.

The salts of boron and beryllium, though being h ghly effective for ringsticking inhibition, are less stable and subject to hydrolysis .and forthis reason are less desirable under conditions where hydrolysis mayoccur. Therefore the preferred group of compounds of this inventioncomprises the salts of the light metals, i. e., metals havingspecificgravities below about 4, and particularly the magnesium salts.

Besides the salts of the above polyvalent metallic and amphotericelements, salts of Zn, Cr, Mn, Cu, Co and Pb are quite effective, theirinhibiting powers in general decreasing with increasing atomic numbersof the metals. In some instances mixtures of several salts containingdifferent metals have given very good results. Salts of the remainingmetals not enumerated above are of less interest, either because theycan be dissolved in mineral lubricating oils with extreme difficultyonly, or because their ring sticking inhibiting powers, althoughpositive, are insufficient for most practical purposes.

Lack of solubility can in many cases be overcome by the addition ofmutual solvents such as alcohols, ethers, esters, fatty acids or similarpolar compounds. For instance clear liquid solutions of lubricating oilscontaining 10 to 20% of magnesium salts of my acids were obtained in thepresence of 10 to 20% excess of the free acids.

I have further found that it is not necessary for the successfulinhibition of piston ring sticking and carbon deposition to add afinished salt of the product of reaction between a fatty acid and anaromatic aldehyde to the lubricating oil, but that it is sufficient todissolve in the oil the several ingredients which under the conditionsof lubrication will apparently combine to form the salts of my inventionheretofore described. Thus whereas the salts of my invention may beproduced by the interaction of aromatic aldehydes with higher fattyacids or their salts, and the salts so produced may be added to thelubricating oils, ring sticking has also been inhibited successfully bydissolving in the lubricating oil small quantities, preferably inapproximate equimolal proportions, of a suitable fatty acid salt and anaromatic aldehyde.

Suitable aromatic aldehydes are, for instance,'

benzaldehyde, naphthaldehyde, anthracenealdehyde,tetrahydronaphthaldehyde, phenyl acetaldehyde, naphthacetaldehyde,phenyl propionic aldehyde, aldehydes in which the aromatic ring or ringscontain alkyl radicals preferably of three or less carbon atoms such astoluyl aldehyde, xylyl aldehyde, prop-yl benzaldehyde, alkylnaphthaldehydes, etc. Instead of aldehydes I may employ chemicallyrelated substances, which upon oxidation are capable of yieldingaldehydes; thus I may use the alcohols corresponding to the abovealdehydes such as benzyl alcohols, naphthyl alcohols, etc., or esters ofthese alcohols, preferably with fatty acids, etc. For example, I haveused a lubricating oil, which normally caused piston rings to stick inless than 100 hours running, for over 1000 hours continuous running byadding thereto sufficient equimolal amounts of magnesium stearate, andbenzyl alcohol or benzyl stearate to yield a theoretical quantity of1.2% magnesium benzyl stearate. Likewise a lubricating oil containing1.0% aluminum stearate and .7% benzyl stearate ran satisfactorily forover 1000 hours.

While I do not wish to be limited to any definite theories, I believethat the fatty acid and the aromatic aldehyde, or the compound capableof yielding such an aldehyde, combine under the lubricating conditionsof internal combustion en-' gines to form the aromatic fatty acid saltsof my invention. However, whether or not the fatty acid salts andaromatic aldehydes, or compounds capable of forming aldehydes, which areindependently dissolved in the oil, actually do combine to form thesalts described earlier, is unformed before or during lubrication andshall' also include the described aromatic fatty acids,

even if produced by other processes than the one described in thisspecification but shall not include compounds in which an aromatic ringis directly attached to the carbon chain of a fatty acid.

' which upon reaction under lubricating conditions matic hydrocarbonradical as a side branch through a link of one or more aliphatic carbonyield the salts, may be used in solution of any type of lubricant whichis otherwise suitable for lubrication. Thus they may be blended withmineral lubricating oils prepared from parafllnic or non-paraiflniccrudes, shale oils, coal tar distillates, etc., by distillation,hydrogenation and/ or solvent extraction, or by polymerizing suitableolefines. If desired suitable lubricating oils may be compounded withfatty oils, various oiliness or extreme pressure compounds, corrosioninhibitors, etc. Y

I claimas my invention:

1. A liquid lubricating oil composition comprising a mineral lubricatingoil and a small amount of a salt combining an element selected from thegroup consisting of polyvalent metallic and =amphoteric elements, with ahigher fatty acid having not more than one double bond in I the carbonchain to which is attachedan aroatoms said small amount being sufficientto inhibit ring sticking when the said composition is used in internalcombustion engines.

2. A liquid lubricating oil composition com:

prising a mineral lubricating oil, and a small amount of a saltcombining an element selected from the group consisting of polyvalentmetallic and amphoteric elements, with a higher saturated fatty acid towhich is attached an aromatic hydrocarbon radical in alpha position as aside branch through a link consisting of one to three aliphatic carbonatoms said small amoimt being suflicient to inhibit ring sticking whenthe said composition is used in internal combustion engines.

3. A liquid lubricating oil composition comprising a mineral lubricatingoil and a small amount of a salt of a polyvale t light metal and anaromatic higher fatty acid'having not more than one double bond in thealiphatic carbon chain to which the aromatic radical is linked as a sidebranch to the fatty acid chain through a link of one or more aliphaticcarbon atoms said small amount being suiilcient toiinhibit ring stickingwhen the said composition is used in internal combustion engines.

v 4. A liquid lubricating oil composition comprisinga minerallubricating oil and a small amount of a magnesium salt of a higher fattyacid having not more than one double bond in the carbon chain to whichis attached an aromatic hydrocarbon radical as a side branch through alink consisting of one to three aliphatic carbon atoms The hereindescribed salts, or compounds said small amount being suflicient toinhibit ring sticking'when the said composition is used in nternalcombuston engines.

5. A liquid lubricating oil composition vcomsticking when the saidcomposition is usedin internal combustion engines.

6. A liquid lubricating oil composition comprising a mineral lubricatingoil and a small amount of aluminum alpha benzal stearate said smallamount being sufiicient to inhibit ring stickingwhen the saidcomposition is used in internal internal combustion engines}.

7. A liquid lubricating oil forinternal combustion engines capable ofretarding piston ring sticking comprising a mineral lubricating oil. i

vwhich contains vfrom'.5 to 2.5% of a'salt combinof polyvalent andamphoteric elements with an aromatic higher fatty acid having not morethan one double bond in the aliphatic carbon chain to which the aromaticradical is attached as a side.

branch to the fatty acid chain through a link of "one or more aliphaticcarbon atoms.

s. A liquid lubricatingoil for internal comb sticking comprising amineral lubricating -oil which contains from .5 to 2.5% of 'a salt of apolyvalent light metal and an aromatic higher tion engines capable ofretarding piston ring I 9. A liquid 'lubri'catingo'il. compositioncomprising a mineral lubricating oil containing small:

amounts of an aromatic aldehyde and a salt combining an element selectedfrom the group consisting of polyvalent metallic and amphoteric elementswith a higher-fatty acid which contains not more than one double bond,said aldehyde being capable of forming a condensation product with saidfatty acid under conditions of lubrication in internal combustionengines, said small amount being suihcient to inhibit ring sticking whenthe said compontion is used in internal oombustion engines.

"10. The composition of claim .9 in which. the aldehyde and the fattyacid salt are contained in the oil in approximate equimolal proportions.

11. The composition of claim 9 in'which the element is magnesium.

12. A liquid lubricating oil composition com prising a minerallubricating oil and a. small amount of a'salt combining an elementselectedfrom the group consisting of polyvalent metallicand amphotericelements with an aromatic fatty acid produced by condensing a higherfatty acid having not more than one double bond in the aliphatic carbonchain and an aromatic aide-- hyde, said small amount being sufllcient toinhibit ring sticking when said composition isused inan internalcombustionengine. I 1

vnauon L. nlcxnrrs.

ing an element selected from the group consisting 3

